Sen. Lamar Alexander (R-Tenn.) continues to aggressively shore up Republican support in an effort to head off a 2014 primary from his right.

The senator’s reelection campaign announced Thursday afternoon that all 13 living former state GOP chairs have agreed to serve as honorary co-chairmen.

“This unprecedented support shows how much Republicans appreciate Lamar Alexander’s leadership as governor and senator in building a conservative grassroots, statewide Republican Party,” Rep. John Duncan (R-Tenn.) said in a statement.

The terms of the 13 Republican chairmen run back to S.L. “Kopie” Kopald, Jr., who held the job from 1971 to 1974.

Under party bylaws, current state Republican chairman Chris Devaney cannot endorse.

Alexander already has locked up the support of the governor, the state’s junior senator and six members of the House delegation. He announced fundraisers last week that he expects will bring in $3 million, in addition to the $1 million he already has stockpiled.